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"In the end all of the interventions came back to the same place - that it might be messy and might be clunky and it might even be a bit untidy but the ceasefire is the only way of really getting a solution ultimately in Syria.

"While it is somewhat two steps forward and one-and-a-half steps back and a little bit of finger-pointing, ultimately everybody came back with the same view: there isn't another way forward.

"This is about the lives of a huge number of people and if the Security Council and the major participants in this dispute can't actually find a resolution then there's blood on the hands of everybody: the Security Council, the Assad Government, those perpetrators who are trying to violate the ceasefire."

US Secretary of State John Kerry made an impassioned response to the speech by Russian counterpart Sergey Lavrov.

Kerry called for the immediate grounding of Syrian and Russian Air Forces in a bid to salvage the ceasefire.

United States Secretary of State John Kerry called for the immediate grounding of Syrian and Russian Air Forces. Photo / NZ Herald

Kerry said the attack raised a profound doubt about whether Russia or the Assad regime would live up to obligations they agreed to in Geneva.

He acknowledge the US-led coalition had hit Syrian forces on Saturday in what was "a terrible accident."

He was setting out the facts because it underscored why "we can't just walk out the door and do business as usual".

The facts required countries to restore credibility to the process, he said.

"That's what critical."

Referring to Lavrov's suggestion there should be no pre-conditions on any talks, Kerry was incensed.

"How can people go sit at a table with a regime that bombs hospitals and drops chlorine gas again and again and again and again and again and again and act with impunity?

"Are you supposed to sit there and have happy talks in Geneva under those circumstances when you've signed up to a ceasefire and you don't adhere to it?

"What kind of credibility do you have with any of your people?"

He said that to restore credibility to the process, "we must move forward to try to immediately ground all aircraft flying in those key areas in order to de-escalate the situation and give a chance for humanitarian assistance to flow unimpeded.

"I emphasise this to Russia. The United States continues to believe there is a way forward that, although rocky and difficult and uncertain, can provide the most viable path out of the carnage," Kerry said.

"If we allow spoilers to choose the path for us, the path of escalation, then make no mistake my friends: the next time we convene here we're going to be facing a Middle East with even more refugees, with more dead, with more displaced, with more extremists and more suffering on an even greater scale."

British Foreign Secretary Boris Johnson said it was important to keep "the precious forward momentum, whatever impetus is left in the Kerry-Lavrov process".

But he said there could be no political process unless there was a genuine ceasefire and there could be no genuine ceasefire unless there was a genuine political agreement to a transition away from the Assad Government.

That regime was responsible for the vast majority of 400,000 deaths; it continued to drop barrel-bombs on its citizens; it dropped "burning, blistering, barbaric chlorine gas" on innocent people and the "monstrous" bombing of aid convoys and medical facilities.

"I hope that we will learn that the court of international opinion will not continue to tolerate this slaughter."

No resolution was passed by the Security Council but Foreign Minister Murray McCully did not rule one emerging soon. The International Syria Support Group will be meeting again on Friday and Lavrov and Kerry would continue talking.

"There are plenty of things we can get agreement on. What we are looking for at the moment is the political will to make that cessation of hostilities stick with a whole of players who have got different agendas."